This invention relates to an optical information recording apparatus typically using two spots efficient for effectuation of an error check mode immediately after recording, and write/read/erase mode.
Conventionally, there have been proposed for use in optical discs a method for realizing an error check function immediately after recording or writing and a method for realizing a write/read/erase function, both the methods utilizing two spots. In the former method, a preceding write spot and a succeeding read or reproduction spot are located close to each other on the same track, and immediately after recording of data by the preceding write spot, the recorded data is read by the succeeding read spot to thereby effect the error check. The latter method is applied to an optical disc wherein a chalcogenide material is used and a laser beam is irradiated on the material to bring it into a crystalline state or an amorphous state so as to effect write/erase of information, in such a manner that a preceding circular read/write spot and a succeeding elliptical erase spot are located close to each other on the same track with a premise that the preceding read/write spot is irradiated in the form of a short-duration light pulse to rapidly heat and cool the material so as to bring it into the amorphous state and the succeeding erase spot is irradiated in the form of a relatively long-duration light pulse to gradually heat and cool the material so as to bring it into the crystalline state, thereby effecting a write/read/erase mode.
In both the methods, however, since the rotation speed of the disc is constant and the distance between the two spots is fixed, linear velocities are different at inner and outer peripheral positions on the disc and the time distance between the two spots becomes different for various positions on the disc. Accordingly, in the case of the error check mode, an error occurs which is due to a timing error for signal reproduction to thereby make the error check invalid and in the case of the write/read/erase mode, the position of a portion to be erased displaces. In particular, when erasing, because of the difference in linear velocity between inner and outer peripheral position on the disc, irradiation periods of time for the beam that erases one recorded pit differ at different positions on the disc, leading to discardant erasing conditions for the inner and outer peripheries on the disc. As a result, the recorded information cannot be erased uniformly and accurately throughout the entire surface of the disc.